1. Field of the Invention
The present invention relates to a sustained-release tablet which can exhibit the effect of pharmaceutically active components contained therein without fail by the administration of one or two times a day, because of its capability of controlling the release rate of the pharmaceutical components with excellent reproducibility.
2. Description of the Background Art
Tablets are a preparation form of drugs which is most widely accepted, because they are more easily administered than capsules and granules.
The increasing demands of reducing the burden imposed to patients by decreasing dosing frequencies of drugs and the requirement of decreasing side effects of drugs by controlling their blood concentration have brought about the recent development in the sustained-release techniques of drug preparations. There have been reports on sustained-release tablets, such as coating tablets coated with a release-controlling coat, matrix tablets comprising water soluble polymeric compounds (Japanese Patent Laid-open (kokai) No. 290818/1988), matrix tablets comprising wax (Japanese Patent Laid-open (kokai) No. 59632/1984), matrix tablets comprising water insoluble polymeric compounds (Japanese Patent Laid-open (kokai) No. 21002/1984), and the like.
All these sustained-release tablets have been with difficulty in controlling the release rate of techniques and studies over a long period time were needed obtain tablets with a desired release rate. Furthermore, the need of complicated processes in the preparation of conventional sustained-release tablets made it difficult to obtain a product with a reproducible release rate. The attempts to obtain tablets with a controlled release rate sometimes encountered with problems in quality control.
Therefore, development of sustained-release tablets which exhibit a controlled release rate, can be manufactured with excellent reproducibility, and can easily ensure the effect of pharmaceutically active components without fail by the administration of one or two times a day has been strongly desired.
In view of this situation, the present inventors have undertaken extensive studies on sustained-release tablets, and have found that a combination of (A) a sustained-release powder comprising an oil component and/or a water insoluble polymer and a pharmaceutically active component and (B) a sustained-release powder comprising a water soluble polymer and a pharmaceutically active component could easily ensure a release rate which is controlled according to the purpose, and that tablets with a reproducible release rate could be manufactured.